1. Field of the Invention
This invention generally relates to explosive compositions and binders and more particularly to RDX/HMX explosive composition which are readily castable.
2. Description of the Prior Art
Previous plastic bonded explosives (PBX) have demonstrated excellent performance and safety properties; however, existing PBX's also demonstrate a residual problem of sporadic irreversible growth during temperature cycling before or after curing. It was determined that tert-butyl hydroperoxide (t-BuOOH), a component of previous PBX compositions, in combination with cobaltous acetylacetonate (CoAA), a catalyst in previous PBX's , causes the irreversible growth. Under conditions, t-BuOOH generates oxygen gas (O.sub.2) as a by-product, and this trapped gas causes the irreversible growth. The mechanistic interpretation of the decomposition reaction is demonstrated in the following equations: ##STR1##
Removing t-BuOOH eliminated the growth problem but increased the tensile modulus of the resulting composition. However, continued curing of the modified composition generates macroperoxy radicals and increases cross linking of the bonder polymers. Post curing at 70.degree. C. for 24 hours accelerates termination of the macroradicals and thus stabilizes the physical characteristics of the modified composition.
More recently two free-radical redox initiation curatives were found suitable as a substitute for the curative involving the use of t-BuOOH. The new curatives are tert-butyl perbenzoate/cuprous bromide (t-BpB/CuBr) and tert-butyl perbenzoate/cobaltous acetyl-acetonate (t-BpB/CoAA), the latter of which is the preferred curative in applicant's invention.
Therefore, there remains a continuing need for a PBX of similar quality and capabilities as that of the prior art that does not exhibit the sporadic irreversible growth during temperature cycling before or after curing.